A more quantitative approach to pasture renewal

The New Zealand dairy industry’s ability to produce milk-based product is reliant on productive pastures, however the performance of pastures often decline over time triggering pasture renewal. On New Zealand dairy farms the level of pasture renewal has been estimated at 6% and 8%, with one analysis suggesting greater levels would benefit the economy. There is little research on how farmers set a renewal level, but we suggest five main drivers: historical, crop requirement, an event response, development and cost/benefit driven. This paper presents a cost/benefit approach to pasture renewal for ‘Willsden’ dairy farm in Canterbury, which has renewed 33% of the property for the last two years with good results. Spray-drilling Italian ryegrass has shown an estimated 2.4 t DM/ha/year extra yield, with an estimated value of $1800/ha less renewal costs of $550/ha. Perennial ryegrass-white clover based sowings were better following an Italian ryegrass crop (estimated value of $1740/ha less renewal costs of $750/ha) than directly from old pasture. Many dairy farmers assess pasture cover weekly, but it is believed few analyse this information to make pasture renewal decisions. There is a significant opportunity for farm systems to profit from this, and for pasture management software developers to provide automated analysis options, to support more quantitative pasture renewal strategies.